<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    #page-menu {
      position: fixed;
      top: 0;
      bottom: 0;
      left: 0;
      width: 220px;
      background: lightgray;
    }
    
    #page-content {
      margin-left: 220px;
    }
  </style>
</head>

<body>
  <div id="page-menu">
    <ul>
      <li>
        <a href="page1">页面1</a>
      </li>
      <li>
        <a href="page2">页面2</a>
      </li>
      <li>
        <a href="page3">页面3</a>
      </li>
    </ul>
  </div>
  <div id="page-content"></div>
  <script src="url-router.js"></script>
  <script src="index.js"></script>
</body>

</html>